Weed Biology and Identification-202 Target students: M .Sc. Students in Weed Science Lecture: Dr. Majid AghaAlikhani (Ph.D.) Academic position : Associate Prof. of Tarbiat Modares University maghaalikhani@modares.ac.ir

Basic Parts of the Plant Roots Stems Leaves Flower

Shoot system Root system

Shoot system Lateral roots Root system Taproot

Shoot system Leaves Stem Lateral roots Root system Taproot

Shoot system Branch Leaves Stem Lateral roots Root system Taproot

Apical bud Lateral bud Shoot system Branch Leaves Stem Lateral roots Root system Taproot

Apical bud Node Lateral bud Internode Node Shoot system Branch Leaves Stem Lateral roots Root system Taproot

Roots 1. Anchor Plant 2. Absorb water and minerals 3. Translocate water and minerals to stem 4. Store Food

Root Structure

Anchorage and support

Storage

Stems 1. Translocate water, minerals and food to the leaves 2. Support the leaves and display them to light 3. Store Food

Woody Dicot Stem Morphology

Transport and support.

Cactus stems store water, photosynthesize.

Stolons produce new individuals at nodes above ground.

Rhizomes produce new individuals at nodes below ground.

Tubers store carbohydrates.

Thorns provide protection.

Leaves 1. Make food through photosynthesis 2. Provide site of gas exchange 3. Store food

Sunlight Shoot system CO2 Transport of water, sugar, and nutrients through vascular tissue Root system Water Nutrients (such as N, P, K)

Make food through photosynthesis

Sloughed-off root cap cells (a) Longitudinal section of root segment Primary Growth Lateral root Cellular Maturation Zone of Root hair (b) Close-up of root tip Vascular tissue Cellular Elongation Zone of Ground tissue Epidermal tissue Zone of Cellular Division Apical mersitem Sloughed-off root cap cells mucilage Root cap

Flowers 1. Contain organs for specialized sexual production 2. Produce seeds and fruit

Different type of Roots A. Tap Root Continuation of the primary root Ideal for anchorage Penetration is greater for water Storage area for food made by photosynthesis

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Different type of Roots B. Fibrous Roots Many finely branched secondary roots Shallow roots cover a large area More effective absorption of water and minerals Roots hold the soil to prevent erosion

Different type of Roots C. Aerial roots Clinging air roots Short roots that grow horizontally from the stems Roots that fasten the plant to a support Absorptive air roots

Different type of Roots Adventitious Roots Develop in places other than nodes Can form on cuttings and rhizomes

Roots Root hairs: Tiny one celled hair like extensions of the epidermal cells located near the tips of the roots where vascular tissues have formed. Increase surface area Absorb water and minerals from soil

Absorbing water and nutrients

Specialized Stems A. Corm (gladiolus, crocus) underground Solid, fleshy, scale covered

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Specialized Stems B. Bulb (tulips, lillies, onions) Layers of fleshy scales that overlap each other Underground stem

Specialized Stems C. Tuber (potato, caladium) Food storage area Short, thick underground stem

Specialized Stems D. Crown (African Violets, fern) Closely grouped stems or plantlets Just above ground or just below

Specialized Stems E. Spurs (pear and apple trees) Short sems found on woody plant limbs adapted for increased production of fruits

Specialized Stems F. Rhizomes (iris, lily of the valley) Underground stems that produce roots on the lower surface and extend leaves and flower shoots above the ground

Specialized Stems G. Stolon (Strawberry, airplane plant) Stem that grows horizontally above the soil surface

Principal Tissues of the Leaf Epidermis Cuticle Waxy substance covers the leaves and stems Waterproof layer that keeps water in plants

Principal Tissues of the Leaf Epidermis (cont) Stomata Openings in the epidermis mainly located on underside of leaves Exchange of gases

Principal Tissues of the Leaf Epidermis (cont) Guard Cells Two cells located on each side of stomata Open and closes stomata

Principal Tissues of the Leaf Mesophyll layer Palisade mesophyll Primary site of photosynthesis Spongy mesophyll Contains air and chloroplasts Site of photosynthesis and gas exchange

Principal Tissues of the Leaf Veins or vascular bundles In spongy mesophyll Phloem tissues conduct food from photosynthesis to rest of plant Xylem tissues conduct water and minerals up to cells in leaves and stems

Parts of the Flower Sepals Outer covering of the flower bud Protects the stamens and pistills when flower is in bud stage

Parts of the Flower Petals Brightly colored Protects stamen and pistills Attracts pollinating insects

Parts of the Flower Stamens Male Reproductive part Anther-produces pollen Filament-supports the anther

Parts of the Flower Pistil Female reproductive part Ovary Enlarged portion at base of pistill Produces ovules which develop into seeds Stigma Holds the pollen grains

Parts of the Flower Style Connects the stigma with ovary Supports the stigma so that it can be pollinated

Complete and Incomplete Flowers Complete: have all four main parts Sepals Petals Stamens Pistils